Added multi-level property functionality
Added tests to check functionality when using multi-level properties
Minor fixes to messages sent from "file in" nodes.

Specifically:

* in the error case, set msg.filename to be the name of the file used (as
  is done in the non-error case),

* in the error case, delete msg.payload so that subsequent nodes only need
  check for a msg.payload to act upon if they don't care about error cases,
  and

* in the non-error case, delete msg.error to avoid passing through errors
  from earlier nodes to a subsequent node that does care about error cases

Messages sent will now always have well-defined behaviour with respect to
the payload, filename, and error in both error and non-error cases.
fix IRC node (once again)
refactoring created incorrect object references - which weren't picked up.
(sorry) -  Addresses Issue 439
Merge pull request #437 from hindessm/file-query-node-usability

Minor fixes to messages sent from "file in" nodes.
Don't let IRC node try to join channels multiple times...
Addresses #447
Allow Raspberry Pi node to set initial output level.
Fix for #443
Also allow (optional) initial read of input pins on deploy.
Moved to Category Raspberry Pi 
(other Pi related nodes will be updated to match soon).
Merge pull request #433 from anna2130/change-node-multi-level-properties

Change node: Multi-level properties